Cards of this type are used as personal identification cards, check cashing cards, drivers licenses, credit cards, payment cards, passport cards and similar certificates of identity. In order to prevent falsifications by partial alterations of the personal data, these cards must, to a large extent, be protected against any separation of the card laminate into the individual layers which carry personal data and, generally, also a photograph of the cardholder.
Identity cards are known which are manufactured in the form of a fused laminate in which a card core carrying the information is protected by transparent films of a different nature from the card core. German Offenlegungsschrift No. 2,308,876 discloses an identity card consisting of a relatively thick carrier film and a thin transparent film, between which there is a special paper having internal features, such as watermarks, banknote printings or the like, which serve as a protection against forgeries and cause differences in the thickness of the paper. The three layers are laminated together in such a way that the internal features are manually, mechanically and/or visually detectable through the transparent film. Further markings which serve to identify the cardholder are provided at a suitable point on this known identity card. For example, a photograph in the form of a film transparency is inserted during lamination between the special paper and the carrier film and is firmly bonded to the special paper. Furthermore, it is possible, at any desired point on the front or rear of the identity card, to laminate onto the outside of the plastic material a strip of special paper, printed according to security technology, as a field for later insertion of signatures or other handwritten entries.
German Auslegeschrift No. 2,163,943 discloses a personal identity card comprising a combination of a support layer, an electrically conductive layer, a barrier layer, a photoconductive layer with an organic photoconductor, an optional cover layer, a protective layer on the photoconductive layer or on the cover layer, a protective layer on the rear of the support layer and an optional cover layer on the last-mentioned protective layer. In this personal identity card, a number of different materials are assembled to produce a laminate which, due to the lack of homogeneity of the individual layers, can be split up so that it is possible to carry out forgeries.
It is apparent that maximum protection against forgeries is achieved by a combination of different security markings and by a card comprising a laminate of layers which resist any attempt to separate them into individual layers and thus prevent any tampering with the information and security markings applied to the layers. For this purpose, German Patent Application No. 28 38 795.3 discloses a composite card core and an upper and a lower cover layer, composed of polymers which are capable of being thermally fused into a laminate. Due to the corresponding consistency of all layers in the laminate, it is impossible to split up such an identity card without destroying the security markings applied to the card core. These security markings include safety prints, for example, made up of intertwined linear patterns, watermarks on papers, photographs of the cardholder and the like. If, contrary to all expectations, someone should succeed in separating the card laminate without damaging the individual layers, it would then be technically easy to counterfeit, imitate or exchange security markings of this kind.
The layers of identity cards of this type are united by laminating at relatively high temperatures and pressures, and this involves the risk of an intolerable melting of the laminates caused by the high temperatures. As a result, the information and/or data on the card may no longer be legible.